We have used serial treadmill exercise echocardiograms in an effort to detect early pulmonary vascular disease. Because of concern that differences in peak estimated TRgradient (estimating pulmonary artery systolic pressure) may reflect differences in workload, rather than progression of disease, we investigated the utility of expressing the change in TRgradient as a function of the achieved workload (METS).
We retrospectively reviewed the reports of the initial and most recent treadmill exercise echocardiograms of 112 patients suspected of PH with a resting TR gradient < 35mmHg on the initial study. We compared the post-exercise changes in TR gradient with the change in TR gradient expressed as a function of workload achieved (METS). For this initial analysis we considered (post-exercise TRgradient - resting TRgradient)/METS > 3 (deltaTRgradient/METS > 3) to be abnormal.
29/112 patients had deltaTRgradient/METS > 3 on F/U echo. 8/29 had progressed to resting TR > 35mmHg (35–45mmHg=6, 45–55mmHg=1, > 55mmHg=1) but 21/29 had resting TR < 35mmHg. With exercise, 6/21pts (29%) increased their TRgradient by 16–25mmHg, 7/21pts (33%) increased their TRgradient by 26–35mmHg, and 8/21pts (38%) increased their TRgradient by > 36mmHg. Comparing deltaTRgradient/METS between the initial study and the present study, 15pts had progressed, 5pts were unchanged and 1pt had improved.
By calculating deltaTRgradient/METS we identified 15 patients who appeared to have had progression of early pulmonary vascular disease, but but who still demonstrated normal resting TRgradients. This ratio should be useful in assessing for progression of early pulmonary vascular disease. With disease progression patients will have a decline in achievable workload on a treadmill exercise test; this will reduce the maximal TRgradient, making it less sensitive as a marker of disease progression. Relating TRgradient to workload should improve the detection of early disease progression.
It is not yet known what parameters measured on treadmill exercise echocardiography provide information regarding risks of disease progression. Relating change in TRgradient to the workload achieved appears helpful. Additional studies, particularly longitudinal (serial) ones, will be necessary to further define the long-term the utility of this measurement.
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